Is North Korea giving missile technology to Iran?

The two countries whose nuclear programs have raised alarms of late may be cooperating more closely than previously known. North Korea agreed six years ago to stop flight-testing longer-range ballistic missiles, which could deliver nuclear or chemical warheads, in exchange for relief from U.S. economic sanctions. Pyongyang still claims it is sticking to the deal, but some Administration officials think it may be cheating by using Iran as its proxy.

Iran's new Shahab-3 medium-range ballistic missile is closely based on North Korea's Nodong missile. After Iran test-fired the Shahab-3 last summer, there have been indications, a top U.S. official says, that...